DIABLO settings

I have just installed a tune with my predator and have a question to the guys who know. I have set the timing to 4 degrees on top and bottom. I havent changed the fuel settings and was wondering if I should. It seems that everyone is setting their fuel at the same time as their spark. The car seems to like the extra spark and is running great. I can get 93 octane here and I think that helps. What could happen if I dont adjust the fuel accordingly??
thanks for the info!! :smile: